CN115072686A - Method for preparing battery-grade iron phosphate by using pyrite cinder - Google Patents
Method for preparing battery-grade iron phosphate by using pyrite cinder Download PDFInfo
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- CN115072686A CN115072686A CN202210615482.6A CN202210615482A CN115072686A CN 115072686 A CN115072686 A CN 115072686A CN 202210615482 A CN202210615482 A CN 202210615482A CN 115072686 A CN115072686 A CN 115072686A
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- solution
- iron
- acid leaching
- ferrous sulfate
- pyrite cinder
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- 238000000034 method Methods 0.000 title claims abstract description 118
- WBJZTOZJJYAKHQ-UHFFFAOYSA-K iron(3+) phosphate Chemical compound [Fe+3].[O-]P([O-])([O-])=O WBJZTOZJJYAKHQ-UHFFFAOYSA-K 0.000 title claims abstract description 54
- 229910000398 iron phosphate Inorganic materials 0.000 title claims abstract description 53
- NIFIFKQPDTWWGU-UHFFFAOYSA-N pyrite Chemical compound [Fe+2].[S-][S-] NIFIFKQPDTWWGU-UHFFFAOYSA-N 0.000 title claims abstract description 47
- 229910052683 pyrite Inorganic materials 0.000 title claims abstract description 47
- 239000011028 pyrite Substances 0.000 title claims abstract description 47
- 239000003818 cinder Substances 0.000 title claims abstract description 46
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 121
- 238000002386 leaching Methods 0.000 claims abstract description 85
- 239000002253 acid Substances 0.000 claims abstract description 72
- 229910052742 iron Inorganic materials 0.000 claims abstract description 56
- 239000011790 ferrous sulphate Substances 0.000 claims abstract description 35
- 235000003891 ferrous sulphate Nutrition 0.000 claims abstract description 35
- 229910000359 iron(II) sulfate Inorganic materials 0.000 claims abstract description 35
- 229910052782 aluminium Inorganic materials 0.000 claims abstract description 21
- 229910001385 heavy metal Inorganic materials 0.000 claims abstract description 19
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims abstract description 18
- 239000012535 impurity Substances 0.000 claims abstract description 15
- 238000011946 reduction process Methods 0.000 claims abstract description 9
- 238000004537 pulping Methods 0.000 claims abstract description 8
- 229910019142 PO4 Inorganic materials 0.000 claims abstract description 7
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 claims abstract description 7
- 239000010452 phosphate Substances 0.000 claims abstract description 7
- 230000002194 synthesizing effect Effects 0.000 claims abstract description 7
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 claims abstract 11
- 239000000243 solution Substances 0.000 claims description 94
- 238000006243 chemical reaction Methods 0.000 claims description 31
- 238000003756 stirring Methods 0.000 claims description 27
- 239000006184 cosolvent Substances 0.000 claims description 22
- KCXVZYZYPLLWCC-UHFFFAOYSA-N EDTA Chemical compound OC(=O)CN(CC(O)=O)CCN(CC(O)=O)CC(O)=O KCXVZYZYPLLWCC-UHFFFAOYSA-N 0.000 claims description 19
- 238000001914 filtration Methods 0.000 claims description 17
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 15
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 15
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 12
- 239000003638 chemical reducing agent Substances 0.000 claims description 9
- 238000002156 mixing Methods 0.000 claims description 9
- 230000035484 reaction time Effects 0.000 claims description 8
- GEHJYWRUCIMESM-UHFFFAOYSA-L sodium sulfite Chemical compound [Na+].[Na+].[O-]S([O-])=O GEHJYWRUCIMESM-UHFFFAOYSA-L 0.000 claims description 8
- 238000005406 washing Methods 0.000 claims description 8
- 239000012065 filter cake Substances 0.000 claims description 6
- 239000011268 mixed slurry Substances 0.000 claims description 6
- 230000001105 regulatory effect Effects 0.000 claims description 6
- FVAUCKIRQBBSSJ-UHFFFAOYSA-M sodium iodide Chemical compound [Na+].[I-] FVAUCKIRQBBSSJ-UHFFFAOYSA-M 0.000 claims description 6
- -1 aluminum ions Chemical class 0.000 claims description 5
- 239000003795 chemical substances by application Substances 0.000 claims description 5
- 150000003017 phosphorus Chemical class 0.000 claims description 5
- 239000012266 salt solution Substances 0.000 claims description 5
- 235000011121 sodium hydroxide Nutrition 0.000 claims description 5
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 claims description 4
- 230000001276 controlling effect Effects 0.000 claims description 4
- 229910052979 sodium sulfide Inorganic materials 0.000 claims description 4
- GRVFOGOEDUUMBP-UHFFFAOYSA-N sodium sulfide (anhydrous) Chemical compound [Na+].[Na+].[S-2] GRVFOGOEDUUMBP-UHFFFAOYSA-N 0.000 claims description 4
- 235000010265 sodium sulphite Nutrition 0.000 claims description 4
- WNROFYMDJYEPJX-UHFFFAOYSA-K aluminium hydroxide Chemical compound [OH-].[OH-].[OH-].[Al+3] WNROFYMDJYEPJX-UHFFFAOYSA-K 0.000 claims description 3
- 238000001354 calcination Methods 0.000 claims description 3
- 238000010790 dilution Methods 0.000 claims description 3
- 239000012895 dilution Substances 0.000 claims description 3
- 238000001035 drying Methods 0.000 claims description 3
- 238000010438 heat treatment Methods 0.000 claims description 3
- 239000002244 precipitate Substances 0.000 claims description 3
- 239000002516 radical scavenger Substances 0.000 claims description 3
- 239000007787 solid Substances 0.000 claims description 3
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims description 2
- 235000011114 ammonium hydroxide Nutrition 0.000 claims description 2
- UYJXRRSPUVSSMN-UHFFFAOYSA-P ammonium sulfide Chemical compound [NH4+].[NH4+].[S-2] UYJXRRSPUVSSMN-UHFFFAOYSA-P 0.000 claims description 2
- DPLVEEXVKBWGHE-UHFFFAOYSA-N potassium sulfide Chemical compound [S-2].[K+].[K+] DPLVEEXVKBWGHE-UHFFFAOYSA-N 0.000 claims description 2
- 229910000029 sodium carbonate Inorganic materials 0.000 claims description 2
- 235000017550 sodium carbonate Nutrition 0.000 claims description 2
- 235000009518 sodium iodide Nutrition 0.000 claims description 2
- AKHNMLFCWUSKQB-UHFFFAOYSA-L sodium thiosulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=S AKHNMLFCWUSKQB-UHFFFAOYSA-L 0.000 claims description 2
- 235000019345 sodium thiosulphate Nutrition 0.000 claims description 2
- UIIMBOGNXHQVGW-UHFFFAOYSA-M Sodium bicarbonate Chemical compound [Na+].OC([O-])=O UIIMBOGNXHQVGW-UHFFFAOYSA-M 0.000 claims 2
- 235000017557 sodium bicarbonate Nutrition 0.000 claims 1
- 229910000030 sodium bicarbonate Inorganic materials 0.000 claims 1
- SURQXAFEQWPFPV-UHFFFAOYSA-L iron(2+) sulfate heptahydrate Chemical compound O.O.O.O.O.O.O.[Fe+2].[O-]S([O-])(=O)=O SURQXAFEQWPFPV-UHFFFAOYSA-L 0.000 description 26
- 230000000052 comparative effect Effects 0.000 description 17
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 12
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 8
- 238000002425 crystallisation Methods 0.000 description 6
- 230000008025 crystallization Effects 0.000 description 6
- 239000012452 mother liquor Substances 0.000 description 5
- 239000001577 tetrasodium phosphonato phosphate Substances 0.000 description 5
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 4
- 239000002994 raw material Substances 0.000 description 4
- GCLGEJMYGQKIIW-UHFFFAOYSA-H sodium hexametaphosphate Chemical compound [Na]OP1(=O)OP(=O)(O[Na])OP(=O)(O[Na])OP(=O)(O[Na])OP(=O)(O[Na])OP(=O)(O[Na])O1 GCLGEJMYGQKIIW-UHFFFAOYSA-H 0.000 description 4
- 235000019982 sodium hexametaphosphate Nutrition 0.000 description 4
- 238000001816 cooling Methods 0.000 description 3
- 238000005554 pickling Methods 0.000 description 3
- 239000000047 product Substances 0.000 description 3
- RSIJVJUOQBWMIM-UHFFFAOYSA-L sodium sulfate decahydrate Chemical compound O.O.O.O.O.O.O.O.O.O.[Na+].[Na+].[O-]S([O-])(=O)=O RSIJVJUOQBWMIM-UHFFFAOYSA-L 0.000 description 3
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 description 2
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 239000006227 byproduct Substances 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 238000004134 energy conservation Methods 0.000 description 2
- 239000007800 oxidant agent Substances 0.000 description 2
- 230000001590 oxidative effect Effects 0.000 description 2
- 238000011084 recovery Methods 0.000 description 2
- 235000002639 sodium chloride Nutrition 0.000 description 2
- 229910052938 sodium sulfate Inorganic materials 0.000 description 2
- 235000011152 sodium sulphate Nutrition 0.000 description 2
- 238000003786 synthesis reaction Methods 0.000 description 2
- 229910018626 Al(OH) Inorganic materials 0.000 description 1
- VTLYFUHAOXGGBS-UHFFFAOYSA-N Fe3+ Chemical compound [Fe+3] VTLYFUHAOXGGBS-UHFFFAOYSA-N 0.000 description 1
- 239000005955 Ferric phosphate Substances 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- UIIMBOGNXHQVGW-DEQYMQKBSA-M Sodium bicarbonate-14C Chemical compound [Na+].O[14C]([O-])=O UIIMBOGNXHQVGW-DEQYMQKBSA-M 0.000 description 1
- 239000010405 anode material Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 238000004880 explosion Methods 0.000 description 1
- 229940032958 ferric phosphate Drugs 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 1
- 229910000399 iron(III) phosphate Inorganic materials 0.000 description 1
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 235000011007 phosphoric acid Nutrition 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 239000002243 precursor Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
- 239000002893 slag Substances 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
- FQENQNTWSFEDLI-UHFFFAOYSA-J sodium diphosphate Chemical compound [Na+].[Na+].[Na+].[Na+].[O-]P([O-])(=O)OP([O-])([O-])=O FQENQNTWSFEDLI-UHFFFAOYSA-J 0.000 description 1
- 229940048086 sodium pyrophosphate Drugs 0.000 description 1
- 230000001502 supplementing effect Effects 0.000 description 1
- 235000019818 tetrasodium diphosphate Nutrition 0.000 description 1
- 238000004065 wastewater treatment Methods 0.000 description 1
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B25/00—Phosphorus; Compounds thereof
- C01B25/16—Oxyacids of phosphorus; Salts thereof
- C01B25/26—Phosphates
- C01B25/37—Phosphates of heavy metals
- C01B25/375—Phosphates of heavy metals of iron
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/80—Compositional purity
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Manufacture And Refinement Of Metals (AREA)
Abstract
The invention provides a method for preparing battery-grade iron phosphate by using pyrite cinder, which is characterized by comprising the following steps of: (1) acid leaching of pyrite cinder: taking pyrite cinder as an iron source, and sequentially performing a pulping process, a primary acid leaching process and a secondary acid leaching process to obtain an iron-containing leaching solution; (2) removing impurities from the iron-containing leachate: sequentially carrying out a reduction process, an aluminum removal process and a heavy metal removal process on the iron-containing leachate to obtain a ferrous sulfate solution; (3) synthesizing iron phosphate: and reacting the ferrous sulfate solution with a phosphate solution to obtain the iron phosphate. The method provided by the invention adopts pyrite cinder as an iron source, can prepare the iron source applicable to preparing battery-grade iron phosphate through a simple acid leaching process and an impurity removal process, can obviously reduce the cost, and is simple in process and easy to industrialize.
Description
Technical Field
The invention relates to the field of batteries, in particular to a method for preparing battery-grade iron phosphate by using pyrite cinder.
Background
The ferric phosphate is a salt produced by an iron source and a phosphorus source, and is a precursor of the new energy anode material lithium iron phosphate; currently, the demand for iron phosphate, a raw material, has been continuously increasing due to the explosion of demand for iron phosphate. As one of raw materials for preparing the iron phosphate: the cost of iron sources is high and therefore it is essential to develop a new process that can produce battery grade iron phosphate from inexpensive raw materials.
A process for producing battery-grade iron phosphate from pyrite cinder as an inexpensive raw material is known, and the pyrite cinder needs to be subjected to acid leaching. The process for acid leaching of pyrite cinder at the present stage mainly comprises the following steps: the direct acid leaching method and the reduction roasting acid leaching method, wherein the direct acid leaching method further comprises the following steps: a mixed acid pickling method, a dissolving-assisting pickling method and a curing pickling method. However, the existing direct acid leaching methods have low leaching rate of iron or harsh conditions, and particularly, some processes introducing chloride ions bring great difficulty to subsequent wastewater treatment and equipment maintenance, so that a process with high leaching rate of iron in pyrite cinder needs to be developed.
Disclosure of Invention
In view of the defects of the leaching process of iron in the pyrite cinder in the prior art, the invention provides a novel method for preparing battery-grade iron phosphate by adopting the pyrite cinder, the leaching process of iron in the pyrite cinder, which is related in the method, belongs to a dissolution-assisting acid leaching method in a direct acid leaching method, and the method can realize the leaching rate of more than 90 percent under mild conditions by only adopting single sulfuric acid for acid leaching and adopting EDTA as a cosolvent; compared with a reduction roasting leaching method, the method has the advantages of simple process, energy conservation and convenient operation; compared with a mixed acid leaching method, the method is a single sulfuric acid system, and does not introduce chloride ions by using hydrochloric acid at the same time like a common mixed acid leaching method; compared with the common dissolution-aiding acid leaching method which adopts phosphoric acid, sodium chloride, sodium pyrophosphate, sodium hexametaphosphate and the like as the cosolvent, the method has good dissolution-aiding effect and high recovery rate of iron; compared with a curing acid leaching method, the process disclosed by the invention is mild in reaction conditions, easy to realize, high in leaching rate and high in resource utilization rate.
The invention provides a method for preparing battery-grade iron phosphate by using pyrite cinder, which comprises the following steps:
(1) acid leaching of pyrite cinder: taking pyrite cinder as an iron source, and sequentially performing a pulping process, a primary acid leaching process and a secondary acid leaching process to obtain an iron-containing leaching solution;
(2) removing impurities from the iron-containing leachate: sequentially carrying out a reduction process, an aluminum removal process and a heavy metal removal process on the iron-containing leachate to obtain a ferrous sulfate solution;
(3) synthesizing iron phosphate: and reacting the ferrous sulfate solution with a phosphate solution to obtain the iron phosphate.
As can be seen from the results of table 6 of the present invention, the leaching rate of iron was significantly improved in example 1 using the co-solvent EDTA, compared to comparative example 1 (the co-solvent used in comparative example 1 was sodium hexametaphosphate), and pyrite cinder was more effectively utilized.
As can be seen from the results in table 7 of the present invention, in the method provided by the present invention, the pyrite cinder is used as the iron source, and the iron source suitable for preparing the battery-grade iron phosphate is prepared through a simple acid leaching process and an impurity removal process, and the prepared battery-grade anhydrous iron phosphate is equivalent to the anhydrous iron phosphate prepared by a conventional process in terms of quality, such that the cost can be significantly reduced, and the process is simple and easy to industrialize.
Drawings
FIG. 1 is a preferred overall process flow diagram of the present invention.
Detailed Description
The invention provides a method for preparing battery-grade iron phosphate by using pyrite cinder, which comprises the following steps:
(1) acid leaching of pyrite cinder: taking pyrite cinder as an iron source, and sequentially performing a pulping process, a primary acid leaching process and a secondary acid leaching process to obtain an iron-containing leaching solution;
(2) removing impurities from the iron-containing leachate: sequentially carrying out a reduction process, an aluminum removal process and a heavy metal removal process on the iron-containing leachate to obtain a ferrous sulfate solution;
(3) synthesizing iron phosphate: and reacting the ferrous sulfate solution with a phosphate solution to obtain the iron phosphate.
Specifically, the overall process flow is as follows:
the whole process flow is as follows:
and (1) acid leaching the pyrite cinder. And (3) taking the pyrite cinder which is a byproduct in the acid preparation from the pyrite as an iron source, and sequentially performing a pulping process, a primary acid leaching process and a secondary acid leaching process to obtain an iron-containing leaching solution.
First, the analysis of the main impurity elements of the pyrite cinder is shown in the following table 1:
TABLE 1
A pulping process. Adding concentrated sulfuric acid solution with the concentration of 90-99 wt%, preferably 98 wt% into the pyrite cinder, and uniformly mixing to obtain mixed slurry. Wherein the acid-solid weight ratio is controlled as follows: (1-5): 1, preferably (1-3): 1, the dripping time of the concentrated sulfuric acid solution is controlled to be 10-120min, preferably 30-90min, and the stirring can be continued for 20-60 min after the addition is finished.
② a primary acid leaching process. And adding pure water and a cosolvent EDTA into the mixed slurry, and uniformly mixing to obtain a primary acid leaching solution.
Wherein, the acid concentration in the primary acid leaching solution is controlled to be 20 wt% -85 wt%, preferably 45-70 wt%, the primary acid leaching solution is heated to 60-100 ℃, preferably 80-100 ℃, the reaction is carried out under stirring, the stirring intensity is preferably 250-350rpm, more preferably 300rpm, and the reaction time is 1-7h, preferably 2-3 h; wherein the addition amount of the cosolvent is 3-8% of the mass of the pyrite cinder.
In the present invention, all the stirring strengths are not particularly limited as long as uniform stirring is possible.
And a secondary acid leaching process. The secondary acid leaching process comprises the following steps: adding pure water into the primary acid leaching solution to control the acid concentration to be 30-45 wt%, the reaction time to be 0.5-2.5h, preferably 1-2h, the reaction temperature and the stirring intensity are in the same stage acid leaching process, and filtering to obtain the iron-containing leaching solution.
The reason for controlling the acid concentration of the reaction system is that the detection of the concentration of iron ions is inconvenient, so the control of the acid concentration controls the concentration of iron ions in the solution, and at the same time, the control also plays a role in reducing the viscosity of the solution, thereby increasing the moving speed of ions in the reaction and reducing the concentration of products to promote the forward progress of the reaction, and the concrete operations are as follows: adding pure water or filtering slag washing water after secondary acid leaching into the reaction solution to control the concentration of acid added into the system to be 30-45 wt%, and the reaction time to be 0.5-2.5h, preferably 1-2h, and then filtering to obtain iron-containing leachate; sampling to measure the content of the ferric iron.
Preferably, the secondary acid leaching step may further include: washing the leached residues after filtration, and reusing the washed washing water instead of pure water in the secondary acid leaching procedure for adjusting the acid concentration; the recycling aims to improve the recovery rate of the pyrite cinder iron.
And (2) removing impurities from the iron-containing leachate. And sequentially carrying out a reduction process, an aluminum removal process and a heavy metal removal process on the iron-containing leachate to obtain a ferrous sulfate solution.
A reduction step. The reduction process comprises: adding a reducing agent into the iron-containing leaching solution, reacting under stirring, and adding Fe in the solution 3+ Reduction to Fe 2+ Obtaining a crude ferrous sulfate solution;
wherein the reducing agent is one or more of sodium sulfite, sodium thiosulfate, sodium iodide and iron powder; the dosage of the reducing agent is 1.05 to 1.5 times of the stoichiometric ratio, preferably 1.1 to 1.3 times; the reaction temperature is normal temperature, the stirring intensity is preferably 250-350rpm, more preferably 300rpm, and the reaction time is 10-30 min.
Taking sodium sulfite as an example of the reducing agent, the main reaction equation generated in the reduction process is as follows:
2Fe 3+ +SO 3 2- +H 2 O＝2Fe 2+ +2H + +SO 4 2-
aluminum removing process: adding a pH regulator into the crude ferrous sulfate solution under stirring, regulating the pH of the solution to 3.5-5.5, preferably 4.5-5.5, completely converting trivalent aluminum ions in the solution into aluminum hydroxide precipitate, continuously stirring for 20-60 min after regulating the pH, and filtering to obtain a solution after removing aluminum;
wherein the pH regulator is one or more of sodium hydroxide, ammonia water, sodium carbonate and sodium bicarbonate, the reaction temperature is normal temperature, and the stirring intensity is preferably 250-350rpm, more preferably 300 rpm.
The main reaction equation occurring during the aluminum removal process is as follows:
Al 3+ +3OH - ＝Al(OH) 3 ↓
and thirdly, heavy metal removing process. Adding a heavy metal trapping agent into the solution after aluminum removal for reaction for 40-90min at 40-60 ℃ under stirring, and then filtering to obtain a pure ferrous sulfate solution;
wherein the heavy metal capture agent comprises one or more of sodium sulfide, potassium sulfide and ammonium sulfide, and the stirring speed is preferably controlled at 350-450rpm, more preferably 400 rpm; the addition amount of the heavy metal scavenger is controlled to be 0.05-1g/L, preferably 0.1-0.7 g/L.
Adjusting the iron concentration. Preferably, the step (2) further comprises: a step of adjusting the iron concentration subsequent to the step of removing heavy metals, the step of adjusting the iron concentration comprising: adding pure water into the ferrous sulfate solution for dilution, and controlling the concentration of the ferrous sulfate in the solution to be 230-kg, preferably 220-kg, of 180-kg, so as to obtain a ferrous sulfate reaction solution for later use.
Synthesizing iron phosphate: and reacting the ferrous sulfate solution with a phosphate solution to obtain the iron phosphate.
The method for synthesizing iron phosphate in the present invention is not particularly limited, and a conventional production method may be employed.
In the invention, industrial phosphoric acid is taken as an example to synthesize the iron phosphate. Specifically, adding sodium hydroxide into phosphoric acid, and adjusting the pH of the solution to 7.0, wherein the oxidant is 20-30 wt% of hydrogen peroxide, and the addition amount of the hydrogen peroxide is 1.13-1.2 times of the reaction amount; adding hydrogen peroxide into a phosphorus salt solution with the pH value of 7.0, and uniformly mixing to obtain a reaction phosphorus salt solution for later use.
During synthesis, the reaction is controlled by the formula (n), (P): and (n), (Fe) ((1-1.05): 1) adding the prepared reaction phosphate solution into the ferrous sulfate solution dropwise by using the ferrous sulfate reaction solution as a base solution, heating to 88-96 ℃ after the dropwise addition is finished, reacting for 1-3h, filtering to obtain an iron phosphate filter cake, washing, drying and calcining the iron phosphate filter cake to obtain the battery-grade anhydrous iron phosphate.
Finally, from the viewpoint of effective utilization of resources and energy conservation and environmental protection, post-treatment can be performed on the iron phosphate mother liquor (the main components are sodium sulfate and EDTA) obtained after filtration, and the post-treatment comprises the following steps: evaporating, concentrating and cooling and crystallizing.
Introducing the iron phosphate mother liquor into mVR for concentration until the solution density is 1.17-1.2g/mL, then injecting the concentrated solution into a crystallization kettle for cooling crystallization, changing sodium sulfate in the solution into sodium sulfate decahydrate crystals for precipitation through cooling crystallization, and centrifuging through a centrifuge to obtain crystallization mother liquor and sodium sulfate decahydrate crystals, wherein the main component of the crystallization mother liquor is a solution containing EDTA, and the crystallization mother liquor can be reused as a cosolvent for the primary acid leaching process; because EDTA is lost in the whole process, when EDTA is reused for leaching again, the leaching rate can reach more than 96% by only supplementing 1-2% of EDTA. In addition, sodium sulfate decahydrate may be sold as a by-product. Thus, the full and effective utilization of resources is completed.
The present invention will be described more specifically by way of examples with reference to FIG. 1.
Example 1
This example illustrates the method for preparing battery-grade iron phosphate from pyrite cinder according to the present invention.
The pyrite cinder used in this example is obtained from pyrite cinder from auspicious cloud group, and the iron content and impurity element analysis thereof are shown in table 2 below:
TABLE 2
(1) Acid leaching of pyrite cinder:
a pulping process. Adding a concentrated sulfuric acid solution with the concentration of 98 wt% into the pyrite cinder, and uniformly mixing to obtain a mixed slurry. Wherein the acid-solid weight ratio is controlled to be 1.7:1, the dripping time of the concentrated sulfuric acid solution is controlled to be 60min, and the stirring can be continued for 20min after the dripping is finished.
② a primary acid leaching process. And adding pure water and a cosolvent EDTA into the mixed slurry, and uniformly mixing to obtain a primary acid leaching solution.
Wherein the acid concentration in the primary acid leaching solution is controlled to be 50 wt%, the primary acid leaching solution is heated to 98 ℃ and reacts under stirring, and the reaction time is 3 hours; wherein the addition amount of the cosolvent is 3 percent of the mass of the pyrite cinder.
And a secondary acid leaching process. The secondary acid leaching process comprises the following steps: adding pure water into the primary acid leaching solution to control the acid concentration to be 40 wt%, reacting for 1h, and filtering to obtain the iron-containing leaching solution.
(2) Removing impurities from the iron-containing leachate:
a reduction step. The reduction process comprises: adding sodium sulfite reducing agent into the iron-containing leachate, reacting under stirring, and adding Fe in the solution 3+ Reduction to Fe 2+ Obtaining a crude ferrous sulfate solution; wherein the dosage of the reducing agent is 1.1 times of the stoichiometric ratio; the reaction temperature was normal temperature, the stirring intensity was 300rpm, and the reaction time was 30 min.
Aluminum removing process: adding a sodium hydroxide pH regulator into the crude ferrous sulfate solution under stirring, regulating the pH of the solution to 5.0, completely converting trivalent aluminum ions in the solution into aluminum hydroxide precipitate, continuously stirring for 20min after regulating the pH, and filtering to obtain a solution after aluminum removal; wherein the reaction temperature is normal temperature, and the stirring intensity is 300 rpm. The impurity element analysis of the solution after the removal of aluminum is shown in the following table 3:
TABLE 3
As can be seen from the comparison between tables 3 and 2, the aluminum content in the solution is greatly reduced through the aluminum removal process.
And thirdly, heavy metal removing process. Adding a sodium sulfide heavy metal trapping agent into the solution after aluminum removal for reaction for 40min at 40 ℃ under stirring, and then filtering to obtain a pure ferrous sulfate solution; wherein the stirring speed is controlled to be 400rpm, and the adding amount of the sodium sulfide heavy metal catching agent is controlled to be 0.5 g/L. The analysis of the impurity elements in the ferrous sulfate solution is shown in table 4 below:
TABLE 4
As can be seen from comparison of tables 4 and 3, the content of each impurity element is further reduced through the heavy metal removal process.
Adjusting the iron concentration. Adding pure water into the ferrous sulfate solution for dilution, and controlling the concentration of ferrous sulfate in the solution to be 200g/kg to obtain a ferrous sulfate reaction solution for later use.
(3) Synthesizing iron phosphate:
adding sodium hydroxide into industrial phosphoric acid, and adjusting the pH value of the solution to 7.0, wherein the oxidant is 20 wt% of hydrogen peroxide, and the addition amount of the hydrogen peroxide is 1.18 times of the reaction amount; adding hydrogen peroxide into a phosphorus salt solution with the pH value of 7.0, and uniformly mixing to obtain a reaction phosphorus salt solution for later use.
During synthesis, the reaction is controlled by the formula (n), (P): and (n), (Fe): 1.02:1, dropwise adding the prepared reaction phosphate solution into the ferrous sulfate solution by taking the ferrous sulfate reaction solution as a base solution, heating to 94 ℃ after dropwise adding, reacting for 2 hours, filtering to obtain an iron phosphate filter cake, and washing, drying and calcining the iron phosphate filter cake to obtain the battery-grade anhydrous iron phosphate.
Examples 2 to 3
These examples are provided to illustrate the method of the present invention for producing battery grade iron phosphate from pyrite cinder.
The same procedure as in example 1 was used to prepare battery grade anhydrous iron phosphate, except that the specific conditions of step (1) in the examples are shown in table 5 below.
TABLE 5
Comparative example 1
Battery grade anhydrous iron phosphate was prepared in the same manner as in example 1, except that the cosolvent EDTA was replaced with the existing cosolvent sodium hexametaphosphate.
Comparative example 2
Battery grade anhydrous iron phosphate was prepared in the same manner as in example 1, except that the amount of EDTA added as a cosolvent was changed from 3% to 1% of the mass of the pyrite cinder.
Comparative example 3
Battery grade anhydrous iron phosphate was prepared in the same manner as in example 1, except that the amount of EDTA added as a cosolvent was changed from 3% to 10% of the mass of the pyrite cinder.
The leaching rates of iron in examples 1 to 3 and comparative examples 1 to 3 were measured, respectively, and the results are shown in table 6 below.
TABLE 6
| Numbering | Leaching rate of iron (%) |
| Example 1 | 90.83 |
| Example 2 | 96.77 |
| Example 3 | 94.12 |
| Comparative example 1 | 78.81 |
| Comparative example 2 | 73.54 |
| Comparative example 3 | 92.34 |
As can be seen from the results in table 6, the leaching rate of iron was significantly improved in example 1 using the co-solvent EDTA, compared to comparative example 1 (comparative example 1 using the existing co-solvent sodium hexametaphosphate), and pyrite cinder could be more effectively utilized.
In addition, compared with the example 1, in the comparative examples 2 to 3, the range of the cosolvent EDTA is not in the preferable range of the cosolvent which is 3 to 8 percent of the quality of the pyrite cinder, namely, the amount of the cosolvent EDTA in the comparative example 2 is too small, and the leaching rate is lower; in the comparative example 3, the cosolvent EDTA is excessive, and the leaching rate is not obviously improved. Therefore, in the invention, the addition amount of the cosolvent EDTA is preferably 3-8% of the quality of the pyrite cinder, considering the comprehensive consideration of the leaching rate and the saving of the use amount of the EDTA.
Comparative example
In this comparative example, battery grade anhydrous iron phosphate was prepared using the same method as in step (3) in example 1, except that ferrous sulfate heptahydrate was used instead of the ferrous sulfate reaction solution prepared in steps (1) to (2) in example 1.
The prepared anhydrous iron phosphate was tested as follows.
The anhydrous iron phosphate products prepared in example 1 and the comparative example were tested, and the test results are shown in table 7.
TABLE 7
As can be seen from the results in table 7, acceptable battery grade iron phosphate products were obtained using the method provided by the present invention, i.e., the results of example 1, with the respective impurity levels approaching those of anhydrous iron phosphate prepared using ferrous sulfate heptahydrate as the iron source. The method provided by the invention adopts pyrite cinder as an iron source, can prepare the qualified iron source applicable to preparing the battery-grade iron phosphate through a simple acid leaching process and an impurity removal process, can obviously reduce the cost, and has simple process and easy industrialization.
Claims (10)
1. A method for preparing battery-grade iron phosphate by using pyrite cinder is characterized by comprising the following steps:
(1) acid leaching of pyrite cinder: taking pyrite cinder as an iron source, and sequentially performing a pulping process, a primary acid leaching process and a secondary acid leaching process to obtain an iron-containing leaching solution;
(2) removing impurities from the iron-containing leachate: sequentially carrying out a reduction process, an aluminum removal process and a heavy metal removal process on the iron-containing leachate to obtain a ferrous sulfate solution;
(3) synthesizing iron phosphate: and reacting the ferrous sulfate solution with a phosphate solution to obtain the iron phosphate.
2. The method according to claim 1, wherein in step (1), the pulping process comprises: adding 90-99 wt% of sulfuric acid solution into the pyrite cinder, and uniformly mixing to obtain mixed slurry;
wherein the acid-solid weight ratio is controlled to be (1-5): 1, preferably (1-3): 1, the dripping time of the sulfuric acid solution is 10-120min, preferably 30-90 min.
3. The method according to claim 1, wherein in step (1), the primary acid leaching process comprises: adding water and a cosolvent EDTA into the mixed slurry, and uniformly mixing to obtain a primary acid leaching solution;
wherein, the acid concentration in the primary acid leaching solution is controlled to be 20-85 wt%, preferably 45-70 wt%; heating the primary acid leaching solution to 60-100 ℃, preferably 80-100 ℃, and reacting under stirring for 1-7 hours, preferably 2-3 hours; the adding amount of the cosolvent is 3-8% of the mass of the pyrite cinder.
4. The method according to claim 1, wherein in step (1), the secondary acid leaching process comprises: adding water into the primary acid leaching solution to control the acid concentration of the system to be 30-45 wt%, and the reaction time to be 0.5-2.5h, preferably 1-2h, and filtering to obtain iron-containing leaching solution.
5. The method according to claim 4, wherein the secondary acid leaching process further comprises: and washing the leached residues after filtration, and reusing the washed washing water in the secondary acid leaching process instead of water to adjust the acid concentration of the system.
6. The method according to claim 1, wherein in the step (2), the reduction process comprises: adding a reducing agent into the iron-containing leaching solution, reacting under stirring, and adding Fe in the solution 3+ Reduction to Fe 2+ Obtaining a crude ferrous sulfate solution;
wherein the reducing agent is one or more of sodium sulfite, sodium thiosulfate, sodium iodide and iron powder; the dosage of the reducing agent is 1.05 to 1.5 times of the stoichiometric ratio, preferably 1.1 to 1.3 times; the reaction time is 10-30 min.
7. The method according to claim 1, wherein in the step (2), the aluminum removing process comprises: adding a pH regulator into the crude ferrous sulfate solution under stirring, regulating the pH of the solution to 3.5-5.5, preferably 4.5-5.5, completely converting trivalent aluminum ions in the solution into aluminum hydroxide precipitate, continuously stirring for 20-60 min after regulating the pH, and filtering to obtain a solution after removing aluminum;
wherein the pH regulator is one or more of sodium hydroxide, ammonia water, sodium carbonate and sodium bicarbonate.
8. The method of claim 1, wherein in step (2), the heavy metal removal process comprises: adding a heavy metal capture agent into the solution after aluminum removal at 40-60 ℃ under stirring for reaction for 40-90min, and then filtering to obtain a ferrous sulfate solution;
wherein the heavy metal scavenger is one or more of sodium sulfide, potassium sulfide and ammonium sulfide, and the addition amount of the heavy metal scavenger is controlled at 0.05-1g/L, preferably 0.1-0.7 g/L.
9. The method of claim 5, further comprising, in step (2): a step of adjusting the iron concentration subsequent to the step of removing heavy metals, the step of adjusting the iron concentration comprising: adding water into the ferrous sulfate solution for dilution, and controlling the concentration of the ferrous sulfate in the solution to be 230-g/kg, preferably 200-220g/kg, so as to obtain the ferrous sulfate reaction solution.
10. The method according to claim 1, wherein in step (3), the ratio of n (P): and (n), (Fe) (1-1.05) and 1, uniformly mixing the ferrous sulfate reaction solution and the phosphorus salt solution, reacting at 88-96 ℃ for 1-3h, filtering to obtain an iron phosphate filter cake, washing, drying and calcining the iron phosphate filter cake to obtain the battery-grade anhydrous iron phosphate.
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| RU2172788C1 (en) * | 2000-07-17 | 2001-08-27 | Институт металлургии Уральского отделения РАН | Method of processing of pyrite cinders |
| CN102730659A (en) * | 2011-04-08 | 2012-10-17 | 江苏绿陵化工集团有限公司 | Method for preparing battery-level ferric phosphate using pyrite cinders |
| CN109368610A (en) * | 2018-10-09 | 2019-02-22 | 湖南雅城新材料有限公司 | A method of using pyrite cinder preparation high-speed rail phosphorus than ferric phosphate |
| CN114014294A (en) * | 2021-12-08 | 2022-02-08 | 高点(深圳)科技有限公司 | Method for preparing lithium iron phosphate by using pyrite and lithium iron phosphate material |
| CN114394581A (en) * | 2022-01-21 | 2022-04-26 | 雅安天蓝新材料科技有限公司 | Iron phosphate dihydrate, preparation method thereof, iron phosphate, lithium iron phosphate and lithium ion battery |
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| RU2172788C1 (en) * | 2000-07-17 | 2001-08-27 | Институт металлургии Уральского отделения РАН | Method of processing of pyrite cinders |
| CN102730659A (en) * | 2011-04-08 | 2012-10-17 | 江苏绿陵化工集团有限公司 | Method for preparing battery-level ferric phosphate using pyrite cinders |
| CN109368610A (en) * | 2018-10-09 | 2019-02-22 | 湖南雅城新材料有限公司 | A method of using pyrite cinder preparation high-speed rail phosphorus than ferric phosphate |
| CN114014294A (en) * | 2021-12-08 | 2022-02-08 | 高点(深圳)科技有限公司 | Method for preparing lithium iron phosphate by using pyrite and lithium iron phosphate material |
| CN114394581A (en) * | 2022-01-21 | 2022-04-26 | 雅安天蓝新材料科技有限公司 | Iron phosphate dihydrate, preparation method thereof, iron phosphate, lithium iron phosphate and lithium ion battery |
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